Stunning tool

ABSTRACT

An improved, highly mobile, easily manipulated impact tool adapted for immobilizing livestock, especially cattle and hogs, comprising a pressure chamber, a pressurized air-actuated piston, valve means for normally preventing air under pressure in the chamber from actuating the piston, and finger controlled trigger means for momentarily opening the valve means for actuating the piston. The trigger means is self-resetting upon release by the finger of an operator. The stunning means is carried by the piston. In one of its forms, the tool has a manually movable sleeve for resetting the piston. In another of its forms, the piston is automatically reset by means of a compression spring. The tool can be gripped comfortably and firmly by an operator, and can be easily maneuvered and aimed to enable an operator to attain optimum accuracy and maximum effectiveness.

United States Patent Willems et al.

[ Mar. 26, 1974 STUNNlNG TOOL [76] Inventors: Donald J. Willems, 3100 S.

Olsander St., Sioux City, Iowa 51 106; Henry A. Spitzley, 564 W. St., Portland, Mich. 48875 [22] Filed: July 26, 1972 [2]] Appl. No; 275,299

[52] US. Cl 17/1 B [51] Int. Cl.....- i A22c 11/00 [58] Field of Search 17/1 B [56] References Cited UNITED STATES PATENTS 3,l27,836 4/!964 Silva l7/l B X 801,839 lO/l905 Behr l7/1 B means for momentarily opening the valve means for actuating the piston. The trigger means is self-resetting upon release by the finger of an operator. The stunning means is carried by the piston. In one of its forms, the tool has a manually movable sleeve for resetting the piston. In another of its forms, the piston is automatically reset by means of a compression spring. The tool can be gripped comfortably and firmly by an operator, and can be easily maneuvered and aimed to enable an operator to attain optimum accuracy and maximum effectiveness.

STUNNING TOOL The present invention relates to an improved impact tool having particular utility in the packing house industry for immobilizing livestock.

Various tools have been developed which have, as one of their main objects, the immobilization of livestock, in particular, cattle and hogs, in a manner which is quick, effective and humane. One such tool is disclosed in U.S. Pat. No. 3,273,657. The tool of that patent is of the impact-triggered type, that is, it is actuated by bringing a movable impact pin into contact with a vital area of an animal to be immobilized. The pin acts to open a valve for releasing air under pressure against a piston. The momentum of the pressurized airdriven piston is transmitted to the impact pin which delivers the immobilizing blow. The tool has been recognized by humane organizations, the packing industry and the United States Government as a significant step forward in achieving effective and humane immobilization of livestock, and, as a result, the tool has been in widespread use.

In accordance with the present invention, an improved impact tool is provided which, apart from its easy maneuverability and excellent mobility, is capable of accurately and instantaneously delivering a high speed immobilizing blow without the need for initially bringing the tool into contact with an animal. The tool is under the complete control of the operator at all times, enabling it to be aimed with precision and to be activated by the operator only when he belives immobilization can be attained most quickly, effectively and humanely. The positive, trigger-controlled, single power stroke action of the tool makes it extremely safe to operate, and results in more efficient use of pressurized air while reducing any recoil to minimum levels. The lightweight, well-balanced contruction of the tool, coupled with its convenient and comfortable gripping handle enables an operator to use the tool for prolonged periods without tiring. The tool is constructed of rugged, longlasting materials, and can be manufactured on an assembly line basis at a relatively low cost.

The improved stunning tool of this invention, in brief, comprises an elongated, substantially cylindrical housing which defines a chamber for receiving air under pressure from a source thereof. Joined to the housing, and extending into the chamber defined thereby, is an elongated, hollow cylinder in which a pressurized airactuated piston is positioned. A valve assembly is provided for the tool for controlling the release of pressurized air from the chamber for actuating the piston. The valve assembly advantageously comprises a normally closed pressurized air operated main valve and a normally closed control, or pilot, valve. Passageway means are provided for the valve assembly which permits highly efficient utilization of pressurized air to effect rapid opening and closure of the valving arrangement while enabling a high speed power stroke to be delivered by the piston. The highly efficient use of pressurized air attained with the tool reduces recoil to minimal levels, and enables the use of a small diameter pressurized air conduit which enhances the mobility and maneuverability of the tool. A finger actuated trigger is provided for momentarily unseating the pilot valve to allow air under pressure from the chamber defined by the housing to open the main valve to enable the piston to be actuated. The trigger, upon release by the finger of the operator, is self-resetting. Thus, the tool delivers a single power stroke, and can only deliver successive power strokes upon release of the trigger, each time, by the operator. Self-actuation of the tool, therefore, cannot inadvertently or accidentally occur under normal operating conditions, a factor which contributes significantly to the safety of the operation of the tool. The pressurized-air actuated piston carries the immobilizing member of the tool. In one form of the tool, a slidable sleeve, having a handle, or knob, thereon, is provided for manually returning the piston to a reset position. In another form of the tool, a compression spring is employed for returning the piston to its initial starting position.

The above and other advantages and features of the invention will be more fully realized and understood from the following description, when taken in conjunction with the accompanying drawings wherein like reference numerals throughout the various views of the drawings are intended to designate similar elements or components.

FIG. 1 is a vertical sectional view of an embodiment of the stunning tool of the present invention showing the valve assembly and the triggering mechanism in normal position for actuation of the piston;

FIG. 2 is a fragmentary vertical sectional view of said embodiment showing the pilot valve of the valve assembly in an open position after it has been unseated by the triggering mechanism of the tool;

FIG. 3 is a fragmentary vertical sectional view of said embodiment showing the main valve in an open position for actuation of the piston, and the position of the triggering mechanism at the end of its stroke, and just prior to release of the trigger by the operator;

FIG. 4 is a vertical sectional view taken substantially along line 4-4 of FIG. 3;

FIG. 5 is a vertical sectional view taken substantially along line 55 of FIG. 1;

FIG. 6 is a vertical sectional view of another embodiment of the stunning tool of the present invention showing the valve assembly and triggering mechanism in position for actuation of the piston;

FIG. 7 is a fragmentary vertical sectional view of the embodiment illustrated in FIG. 6 showing the main valve in an open position, and the position of the triggering mechanism at the end of its stroke;

FIG. 8 is a vertical sectional view taken substantially along line 8-8 of FIG. 6;

FIG. 9 is a vertical sectional view taken substantially along line 99 of FIG. 6; and

FIG. 10 is a vertical sectional view taken substantially along line 10-10 of FIG. 6.

Referring, now, in particular, to FIGS. 1 through 5 of the drawings, the embodiment of the tool, designated generally by reference numeral 10, as shown, has an overall, pistol-like appearance, and comprises an elongated, hollow, substantially cylindrical housing 12 having an opening 12a at the front end thereof and an opening 12b at the rear end thereof. The housing 12 defines a chamber 14 for receiving air under pressure from a source thereof. To this end, the housing 12 is provided with an internally threaded extension 12c in which a threadedfitting 16 is engaged. The fitting 16, in turn, is connected to a flexible hose 18 through which air under pressure is conveyed to the chamber 14 from a source (not shown) thereof.

Joined to the housing 12, and extending through the opening 12a in the front end thereof into the chamber 14, is an elongated, hollow, open-ended cylinder 20. In

the embodiment of the tool illustrated, the cylinder is secured to the housing 12 by providing the cylinder 20 with an annular, outwardly extending flange 200 having a plurality of tapped openings 20b20b therethrough, which are in register with corresponding tapped openings 12d 12d in the front wall of the housing 12, for receiving screws 2222.

Positioned within the cylinder 20 is a free-moving piston 24 provided with a central, threaded opening 240 in which is engaged the externally threaded end of an impact rod or pin 26. The free, or leading end 26a of the pin 26 is chisel-shaped to enhance the stunning action of the pin. As best seen in FlGS. 1 through 3, the outer wall of the piston 24 has an annular groove 24b formed therein for engaging a snap ring 28 positioned in an annular groove 200 formed in the inner wall of the cylinder 20 at the rear end thereof. The snap ring 28, when engaged in the groove 24!) of the piston 24, acts to maintain the piston 24, and its associated impact pin 26, in a pre-set, or operative, position in the cylinder 20.

Also positioned within the cylinder 20, at the front end thereof, is an impact pin guide sleeve 32. The sleeve 32 is provided with a stop flange 320 at its inner end, the function of which will become clear as the description proceeds, and a retaining flange 32b at its muzzle, or outer, end. As shown, the sleeve 32 is se cured in position at the front end of the cylinder 20 by a threaded cap member 34. The cap member 34 has an inwardly extending annular lip 340 which holds the flange 32b of the guide sleeve 32 in abutting relation to the front end of the cylinder 20.

A movable, piston return sleeve 36, having a diameter slightly less than the internal diameter of the cylinder 20 and slightly greater than the diameter of the inner end of the guide sleeve 32 as measured across the stop flange 32a thereof, also is positioned within the cylinder 20. The sleeve 36 is conveniently moved by a finger knob, or handle, 38 which extends through a longitudinal slot 42 formed in the wall of the cylinder 20. The sleeve 36, and its associated knob, or handle 38, serve to reset the piston 24 after each power stroke. The slot 42, apart from enabling the piston 24 to be moved to a reset position, also acts as a vent for unspent pressurized air in the cylinder 20. The position of the sleeve 36 both at the end of the power stroke of the piston 24, and after the piston 24 has been reset, is clearly shown in FIG. 1 of the drawings.

An impact cushion or bumper element 44 is provided inthe cylinder 20 to absorb and dissipate the momentum of the piston 24 at the end of its power stroke. The cushion or bumper element 44, as shown, comprises a plurality'of stacked, discs 44a each having a central opening for receiving the impact pin 26. The discs 44a are carried on a washer-like support member 44b, and may be fabricated of a resilient material such as neoprene, or the like.

A valve assembly 50 is secured to the inner end of the cylinder 20, within the chamber 14 defined by the housing 12. The assembly 50 comprises a main valve housing 52, having an enlarged, substantially cylindrical front portion 52a, provided with internal threads for engagement with external threads on the inner end of the cylinder 20, and a back portion 52b provided with external threads for engagement with a threaded cap member 54. The cap member 54, in turn, is threadedly engaged with a pilot valve seat member 56. As illustrated, the threaded front end of the pilot valve seat member 56 extends through the opening 121) in the rear wall of the housing 12 to engage the cap member 54, and acts to securely support the valve assembly 50 within the housing 12.

The front portion 520 of the main valve housing 52 defines a chamber 58 which communicates with the chamber 14 defined by the housing 12 through ports, or openings 6060 in the side wall thereof. Positioned within the chamber 58 is a main valve seat 62 having a pair of inwardly extending projections 64-64 which engage the piston 24, and serve as stops, when the piston 24 is returned to its reset position by the movable sleeve 36. A main valve 66, carried by the body portion 68a of a valve piston 68, is positioned in the chamber 58, and is secured to the body portion 68a of the piston 68 by a lock nut 70. A compression spring 72 is provided in the chamber 58 to maintain the main valve 66 in a normally closed position as shown in FIG. 1.

The head portion 68b of the valve piston 68 rides in a chamber 74 defined by the rear portion 52b of the housing 52 and a valve piston guide partition 52c which separates the front portion 520 from the rear portion 52b of the housing 52. The head portion 68b has a restricted longitudinal passageway 76 formed therein which communicates with the chamber 14 through ports or openings 78-78 formed in the side wall of the rear portion 52b of the housing 52. As best seen in FIGS. 1 and 2 of the drawings, when the main valve 66 is in a normally closed position, the front face of the head portion 68b of the valve piston 68 is maintained in spaced relation with respect to the valve piston guide partition 52c of the housing 52. The space 82 thus formed between the partition 52c and the front face of the head portion 680 enables air under pressure to pass from the chamber 14, through the ports 7878 in the side wall of the rear portion 52b of the housing 52, into the space 82, through the restricted passageway 76 in the head portion 68b of the valve piston 68, and into the main area of the chamber 74.

The body portion 68a of the valve piston 68 has a longitudinal bore 84 formed therein which receives the leading end of a valve stem 86 which carries a control, or pilot valve 88. The pilot valve 88 is maintained in a normally closed position by a compression spring 90. The rearward end 86a of the valve stem 86 extends through a central opening 92 in the pilot valve seat member 56.

As illustrated in FIGS. 1 through 5, momentary unseating, or opening, of the pilot valve 88, and the resultant opening of the main valve 66 for actuation of the piston 24, is achieved by means of a triggering mechanism. As shown, the triggering mechanism comprises a movable shaft 94 which extends through, and is movable in, a transverse bore 96 formed in a handle 98 by means of which the tool 10 is conveniently manipulated and aimed by an operator. A trigger finger engaging plate 102 is secured to the leading end of the shaft 94. The threaded end of a rod 104 is secured in the back end of the shaft 94. The rod 104 carries a compression spring 106, and is supported at its free end by one end of a metal support strip 108 which is secured to the housing 12 by a screw 110. The rod 104 has a bifurcated end portion 1040 on which a scar 112 is pivotally mounted. The sear 112 is stepped or notched at its free end where it engages the lower end of a lever 114. A leaf spring 116, anchored to the bifurcated end portion 104a by a screw 118, urges the sear 112 into engagement with the lower end of the lever 114. The lever 114 is mounted for pivotal movement on a pin 120 held in the curled, bifurcated upper end 108a of the support strip 108. The upper end of the lever 114 is stepped, or notched, and is adapted to engage the rearward end 86a of the valve stem 86 when the trigger mechanism is actuated by an operator. The lever 114 has an adjustable stop bolt or pin 122 for regulating the position of the lower end of the lever 114 with relation to the notched portion of the sear 112. A trigger mechanism guard 124, as well as a trigger guard 126, are provided for the tool to protect against possible inadvertent actuation of the tool, when the tool is not being held by an operator; or when it is accidentally dropped, or dislodged from the operators hand.

In operation, the tool 10 is grasped by the hand of an operator, and aimed at a target which is in proximity to the front, or muzzle end of the impact pin guide sleeve 32. The air pressure in the chambers 14, 58 and 74, and the space 82, is essentially equal prior to actuation of the triggering mechanism by the operator, and the main valve 66 and the control, or pilot valve 88 are in a normally closed position as illustrated in FIG. 1 of the drawings. When the movable shaft-94 of the triggering mechanism is moved rearwardly by a force applied by the finger of the operator on the plate 102, the notched end of the sear 112 acts against the lower end of the lever 114 to cause the upper end of the lever 114 to pivot into engagement with the rearward end 86a of the valve stem 86, thereby unseating the control or pilot valve 88. The air pressure imbalance between the chamber 74 and the space 82 resulting from the momentary unseating of the control, or pilot valve 88, causes the valve piston 68 to move in the direction of the pilot valve 88, and to unseat the main valve 66. Air under pressure from the chamber 14 thereupon acts against the piston 24 and propels it, and its associated impact pin 26, rapidly forward. Any unspent momentum of the piston24 is absorbed and dissipated by the bumper element 44, and unspent pressurized air is vented through the slot 42 in the cylinder 20. As the valve piston 68 moves in a rearward direction, the compression springs 72 and 90 are compressed. Compression of the spring 90 acts to reseat the control, or pilot valve 88 and causes the rearward portion 86a of the valve stem 86 to pivot the lever 114 to a stop position as shown in FIG. 3 of the drawings. The lower end of the lever 114 has, at this point, become disengaged from the sear 112. Air pressure on both sides of the head portion 68b of the valve piston 68 is quickly equalized by means of the restricted, longitudinal passageway 76 in the head portion 68b. As a result, the compressed springs 72' and 90 can exert a force on the portions 68a and 68b of the valve piston 68 which causes the main valve 66 to rapidly close. Upon release of the triggering mechanism by the finger of the operator, the spring 106, carried on the rod 104, returns the sear 112 to a forward position, into engagement with the lower end of the lever 114 as shown in FIG. 1. The piston 24 is reset for delivery for another power stroke by moving the sleeve 36 rearwardly by means of the handle or knob 38 until the snap ring 28 is engaged in the annular groove 24b of the piston 24. This arrangement enables the tool to be operated with maximum safety, while achieving optimum use of pressurized air and reducing recoil to minimal levels. In addition, as stated hereinabove, the more effective'utilization of the pressurized air permits the use of a smaller diameter supply hose 18 thereby enhancing the maneuverability and mobility of the tool.

In FIGS. 6 through 10 of the drawings, another embodiment of the stunning tool of the present invention is illustrated. The tool there shown is particularly adapted for delivering an immobilizing blow to hogs. It is clear from the drawings that the tool, designated generally by reference numeral 210 in FIGS. 6 and 7, has numerous elements and components in common with the tool 10 illustrated in FIGS. 1 through 5 of the drawings. In recognition of this fact, and to facilitate the description of the tool 210, the last two numbers of the reference numerals employed in the description to follow will correspond to the reference numerals used to designate similar elements or components of the tool 10.

The tool 210, as illustrated, is adapted to be held by both hands of an operator, and is, therefore, contoured differently from the tool 10. Like the tool 10, the tool 210 comprises an elongated, hollow, substantially cylindrical housing 212 having an opening 2120 at the front end thereof and opening 212b at the back end thereof. The housing 212 defines a chamber 214 for receiving air under pressure from a source thereof. As illustrated, pressurized air is supplied to the chamber 214 through an L-shaped nipple 215 which is connectable to a flexible hose (not shown) leading to a source (not shown) of air under pressure.

Joined to the housing 212, and extending through the opening 212a in the front end thereof into the chamber 214, is an elongated, open-ended cylinder 220. As shown, the cylinder 220 is connected to the housing 212 by providing threads on the end wall of the housing 212 and an extension 221 of an annular flange 22011 on the cylinder 220. The cylinder 220 has a plurality of air vents, or ports 223223 formed in the wall thereof adjacent to the flange 220a. A blade guide head 225 is secured to the threaded leading end of the cylinder 220 by a threaded connector 227. As best seen in FIG. 10 of the drawings, the blade guide head 225 has an opening 225a therethrough, the shape of which is designed to accommodate the immobilizing element of the tool 210.

Positioned within the cylinder 220 is a piston 224 which carries a rod or pin 226. Secured, as by welding, to the rod or pin 226 is a blade 229 having a concave leading edge 2290. The blade 229 has a chisel-like configuration, and is capable of performing a stunning, severing, and sticking operation with a single stroke.

Also positioned within the cylinder 220 is an elongated, piston return, or reset spring 231, the function of which will be made clear as the description proceeds. Like-the tool 10, the cylinder 220 of the tool 210, has a bumper element 244 therein to absorb and dissipate the momentum of the piston 224 at the end of its power stroke.

As in the case of the tool 10, the tool 210 has a valve assembly 250 secured to the inner end of the cylinder 220, within the chamber 214. Like the valve assembly 50, the assembly 250 comprises a main valve housing 252 having a front portion 252a provided with internal threads for engagement with external threads on the inner end of the cylinder 220, and a rear portion 252b provided with external threads for engagement with a threaded cap member 254. The cap member 254, in turn, is connected to a pilot valve seat member 256. As in the valve assembly 50 of the tool 10, the threaded front end of the seat member 256 extends through the opening 212b in the rear wall of the housing 212 to engage the cap member 254, and acts to rigidly support the valve assembly 250 within the chamber 214 of the housing 212.

The main valve housing 252 defines a chamber 258 which communicates with the chamber 214 through ports or openings 260260. A main valve seat 262 and a main valve 266 also are provided for the assembly 250. The main valve 266 is secured to the body portion 268a of a valve piston 268 by a lock nut 270. A compression spring 272 is positioned in the chamber 258 to maintain the main valve 266 in a normally closed condition.

The valve piston 268 has a head portion 2681; which rides in a chamber 274 defined by the back portion 252b of the housing 252 and a valve piston guide partition 2520. The head portion 268!) of the valve piston 268 has a restricted, longitudinal passageway 276 formed therethrough which communicates with the chamber 214 through ports or openings 278278. As with the valve assembly 50, the head portion 268a of the valve piston 268 is maintained in spaced relation to the valve piston guide partition 252C in the valve housing 252. The space 282 thus formed enables pressurized air to pass from the chamber 214 into the chamber 274 as described in connection with the valve assembly 50.

The body portion 268a of the valve piston 268 has a longitudinal bore 284 for receiving the leading end of a valve stem 286. The stem 286 carries a control, or pilot valve 288. A compression spring 290 maintains the pilot valve 288 in a normally closed position. The rearward end 286a of the valve stem 286 extends through a central opening 292 in the pilot valve seat member 256.

Like the tool 10, the tool 210 is actuated by a triggering mechanism. The triggering mechanism of the tool 210, as shown, comprises an L-shaped trigger member 293, the finger engaging leg 293a of which carries a guide pin 295 which rides in a transverse bore 297 in a handle 298. The leg 2930 also carries a return spring 306, the lower end of which is retained in position on the leg 293a by an extension 307, while the upper end of the spring 306 is engaged in a transverse bore 309 formed in the handle 298. The other leg 29312 of the trigger member 293 carries a pivotally mounted sear 312, the downwardly extending end of which is hookshaped or notched for engaging one end of a pivotally mounted rocker arm or lever 314. A leaf spring 316 is secured to the leg 293b for urging the notched end of the sear 312 into engagement with the sear engaging end of the lever 314. The other end of the lever 314 is positioned adjacent to the rearwardly extending portion 286a of the valve stem 286, and acts to unseat the pilot valve 288 when the triggering mechanism is actuated. The leg 293b also has a rearwardly extending guide pin 315 which rides in a slot 317 formed in a trigger mechanism guard housing 324.

The sear 312 has an inwardly extending arm 312a which is adapted to engage a trip-bar 325 whereby the sear 312 is pivoted to a position to disengage the notched end thereof from the sear-engaging end of the lever 314. The upper end of the sear 312 has a rearwardly extending stop arm 312b which engages the leg 2931; of the trigger member 293, and controls the forward extent to which the spring 316 is able to urge the notched, lever engaging end of the sear 312. A stop pin 329 is provided on the lever support member 331 to maintain the sear-engaging end of the lever 314 at a position whereby it can be re-engaged by the notched end of the sear 312 after the finger engaging leg 293a of the triggering mechanism has been released by the operator. As indicated hereinabove, an auxiliary, or second handle 327 is provided for the tool 210 for greater ease in handling and aiming the tool.

Except for the automatic resetting feature of the tool 210, the operation thereof is substantially the same as the operation of the tool 10. An operator grasps the handle 298 in one hand and the auxiliary or second handle 327 in the other hand. The tool is aimed at a target area, and the pilot valve 288 is momentarily opened by actuating the triggering mechanism. Unseating of the pilot valve 288 results in a pressure imbalance on the front and rear faces of the head portion 268a of the valve piston 268, causing the piston 268 to move in the direction of the pilot valve 288 and to open the main valve 266. The piston 224, and its associated blade 229, is rapidly propelled forward against the bias of the return or reset spring 231 to deliver a quick, effective immobilizing blow. The extent of travel of the piston 224 is controlled by the inner end of the blade guide 225 with which the bumper element 244 makes contact as the piston 224 delivers its power stroke. At the completion of the power stroke of the piston 224, the spring 231 acts to automatically return the piston 224 to its starting position. Unspent air is vented through the openings or ports 223 in the cylinder 220 thereby eliminating any air pressure build-up behind the piston 224. Although the piston 224 is automatically reset by the action of the spring 231, the piston 224 cannot be made to deliver another power stroite until the trigger mechanism has been released by the operator to enable the sear 312 to re-engage the sear-engaging end of the lever 314.

Air pressures utilized in the operation of the stunning tool of this invention are variable, and will depend, in the main, on the use to which it is put. Thus, when used for stunning cattle, air pressures of the order of from about l60 to about 200 pounds per square inch are satisfactory. The air pressure may be regulated as desired by any suitable means such as an air line pressure regulator, or by connecting the tool to a constant air pressure source.

While for purposes of illustration, specific forms of this invention have been disclosed and described in detail in relation to their use as stunning or impact tools for immobilizing livestock, other forms, and uses, thereof will become apparent to those skilled in the art upon reference to this disclosure and, therefore, this invention is to be limited only by the scope of the appended claims.

What is claimed is:

1. A stunning tool for use in immobilizing livestock comprising a housing defining a chamber for receiving air under pressure from a source thereof, piston guide means joined to the housing and communicating with the chamber defined by the housing, a pressurized airactuated piston adapted for reciprocal movement in the piston guide means, valve means for normally preventing air under pressure in the chamber defined by the housing from actuating the piston, said valve means including a normally closed main valve and a normally closed pilot valve, finger actuated trigger means for momentarily moving the pilot valve from its normally closed position to an open position, said trigger means being self-resetting upon release by the finger of an operator, passageway means communicating with the chamber defined by the housing for enabling air under pressure from the chamber to open the main valve when the pilot valve is momentarily moved to an open position by the trigger means for actuating the piston, stunning means actuated by the piston for delivering an immobilizing blow, and valve reseating means associated with said valve means for automatically returning the main valve and the pilot valve to their normally I closed position.

2. A tool according to claim 1 wherein the valve means includes a valve housing having passageways therethrough which communicate with the pressurized air receiving chamber, and a pressurized air actuated valve piston in the valve housing for moving the main valve to an open position.

3. A tool according to claim 2 wherein the valve housing comprises a main valve chamber and a pilot valve chamber separated by a valve piston guide partition, the valve piston in the valve housing having a body portion which carries the main valve and a head portion which is adapted for reciprocal movement in the pilot valve chamber.

4. A tool according to claim 3 wherein the head portion of the valve assembly has a restricted passageway therethrough which is in communication with the pressurized air receiving chamber and the pilot valve chamber of the valve housing.

5. A tool according to claim 1 wherein the valve re seating means comprises spring means in the valve housing for returning the main valve and the pilot valve to their normally closed position.

6. A tool according to claim 1 wherein the trigger means comprises a pivotal lever, one end of which is adapted to engage pilot valve unseating means, and the other end of which is adapted to engage lever pivoting means.

7. A tool according to claim 6 wherein the pilot valve unseating means comprises a valve stem in contact with the pilot valve.

8. A tool according to claim 6 wherein the lever pivoting means comprises a pivotally mounted catch connected to a finger actuated trigger.

9. A tool according to claim 8 wherein the pivotally mounted catch and the finger actuated trigger are associated with spring means to enable the catch to reengage the pivotal lever after the trigger has been released by an operator of the tool following each successive operation thereof.

10. A tool according to claim 6 wherein adjustable stop means is provided to control the extent of the pivotal movement of the pivotal lever.

11. A tool according to claim 1 wherein hand manipulated piston reset means is provided for returning the piston to an operative piston after each power stroke.

12. A tool according to claim 11 wherein the piston reset means comprises a movable sleeve having a handle joined thereto, said sleeve being positioned in the piston guide means of the tool.

13. A tool according to claim 12 wherein the handle extends outwardly from a longitudinal slot in the piston guide means.

14. A tool according to claim 1 wherein a return spring is positioned in the piston guide means for automatically resetting the piston after each power stroke.

15. A tool according to claim 1 wherein the pressurized air-actuated piston is free-moving, and releasable piston retaining means is provided in the piston guide means for supporting the piston in an operative position.

16. A tool according to claim 1 wherein the stunning means comprises an elongated rod connected to the piston, said rod having a concave-shaped impact end.

17. A tool according to claim 1 wherein the stunning means comprises an elongated chisel-like blade having a concave edge portion at the leading or impact end thereof.

18. A tool according to claim 1 wherein a pistol grip handle is provided for the tool, in proximity to the finger actuated trigger means thereof, to enable an operator to grasp and aim the tool at a target with one hand.

19. A tool according to claim 1 wherein two handles are provided for the tool to enable an operator to support and aim the tool with the aid of both of his hands.

20. A stunning tool for use in immobilizing livestock comprising a main housing defining a chamber for receiving air under pressure from a source thereof, a cylinder joined to the main housing and extending into the chamber defined by the main housing, a pressurized air-actuated piston adapted for reciprocal movement in the cylinder, a valve assembly in the main housing for normally preventing air under pressure in the chamber defined by the main housing from actuating the piston, said valve assembly including a normally closed main valve and a normally closed pilot valve, a pressurized air-actuated valve piston for opening the main valve, finger actuated trigger means for momentarily moving the pilot valve from its normally closed position to an open position, said trigger means being self-resetting upon release by the finger of an operator, passageway means communicating with the valve assembly and the chamber defined by the main housing for enabling air under pressure from the chamber to actuate the valve piston and open the main valve when the pilot valve is momentarily moved to an open position by the trigger means for actuating the piston, stunning means actuated by the piston for delivering an immobilizing blow, valve reseating means associated with the valve assembly for automatically returning the main valve and the pilot valve to their normally closed position, and a handle for the tool to enable an operatorto support, aim and operate the tool with one hand.

21. A stunning tool for use in immobilizing livestock comprising a main housing defining a chamber for receiving air under pressure from a source thereof, a cyl inder joined to the main housing and extending into the chamber defined by the housing, a pressurized airactuated piston adapted for reciprocal movement in the cylinder, a valve assembly in the main housing for normally preventing air under pressure in the chamber defined by the housing from actuating the piston, said valve assembly including a normally closed main valve and a normally closed pilot valve, a pressurized airactuated valve piston for opening the main valve, finger actuated trigger means for momentarily moving the pilot valve from its normally closed position to an open position, said trigger means being self-resetting upon release by the finger of operator, passageway means communicating with the valve assembly and the chamber defined by the main housing for enabling air under pressure from the chamber to actuate the valve piston and open the main valve when the pilot valve is momentarily moved to an open position by the trigger means for actuating the piston, stunning means actuated by the piston for delivering an immobilizing blow, piston return means for automatically resetting the pis- 

1. A stunning tool for use in immobilizing livestock comprising a housing defining a chamber for receiving air under pressure from a source thereof, piston guide means joined to the housing and communicating with the chamber defined by the housing, a pressurized air-actuated piston adapted for reciprocal movement in the piston guide means, valve means for normally preventing air under pressure in the chamber defined by the housing from actuating the piston, said valve means including a normally closed main valve and a normally closed pilot valve, finger actuated trigger means for momentarily moving the pilot valve from its normally closed position to an open position, said trigger means being self-resetting upon release by the finger of an operator, passageway means communicating with the chamber defined by the housing for enabling air under pressure from the chamber to open the main valve when the pilot valve is momentarily moved to an open position by the trigger means for actuating the piston, stunning means actuated by the piston for delivering an immobilizing blow, and valve reseating means associated with said valve means for automatically returning the main valve and the pilot valve to their normally closed position.
 2. A tool according to claim 1 wherein the valve means includes a valve housing having passageways therethrough which communicate with the pressurized air receiving chamber, and a pressurized air actuated valve piston in the valve housing for moving the main valve to an open position.
 3. A tool according to claim 2 wherein the valve housing comprises a main valve chamber and a pilot valve chamber separated by a valve piston guide partition, the valve piston in the valve housing having a body portion which carries the main valve and a head portion which is adapted for reciprocal movement in the pilot valve chamber.
 4. A tool according to claim 3 wherein the head portion of the valve assembly has a restricted passageway therethrough which is in communication with the pressurized air receiving chamber and the pilot valve chamber of the valve housing.
 5. A tool according to claim 1 wherein the valve reseating means comprises spring means in the valve housing for returning the main valve and the pilot valve to their normally closed position.
 6. A tool according to claim 1 wherein the trigger means comprises a pivotal lever, one end of which is adapted to engage pilot valve unseating means, and the other end of which is adapted to engage lever pivoting means.
 7. A tool according to claim 6 wherein the pilot valve unseating means comprises a valve stem in contact with the pilot valve.
 8. A tool according to claim 6 wherein the lever pivoting means comprises a pivotally mounted catch connected to a finger actuated trigger.
 9. A tool according to claim 8 wherein the pivotally mounted catch and the finger actuated trigger are associated with spring means to enable the catch to re-engage the pivotal lever after the trigger has been released by an operator of the tool following each successive operation thereof.
 10. A tool according to claim 6 wherein adjustable stop means is provided to control the extent of the pivotal movement of the pivotal lever.
 11. A tool according to claim 1 wherein hand manipulated piston reset means is provided for returning the piston to an operative piston after each power stroke.
 12. A tool according to claim 11 wherein the piston reset means comprises a movable sleeve having a handle joined thereto, said sleeve being positioned in the piston guide means of the tool.
 13. A tool according to claim 12 wherein the handle extends outwardly from a longitudinal slot in the piston guide means.
 14. A tool according to claim 1 wherein a return spring is positioned in the piston guide means for automatically resetting the piston after each power stroke.
 15. A tool according to claim 1 wherein the pressurized air-actuated piston is free-moving, and releasable piston retaining means is provided in the piston guide means for supporting the piston in an operative position.
 16. A tool according to claim 1 wherein the stunning means comprises an elongated rod connected to the piston, said rod having a concave-shaped impact end.
 17. A tool according to claim 1 wherein the stunning means comprises an elongated chisel-like blade having a concave edge portion at the leading or impact end thereof.
 18. A tool according to claim 1 wherein a pistol grip handle is provided for the tool, in proximity to the finger actuated trigger means thereof, to enable an operator to grasp and aim the tool at a target with one hand.
 19. A tool according to claim 1 wherein two handles are provided for the tool to enable an operator to support and aim the tool with the aid of both of his hands.
 20. A stunning tool for use in immobilizing livestock comprising a main housing defining a chamber for receiving air under pressure from a source thereof, a cylinder joined to the main housing and extending into the chamber defined by the main housing, a pressurized air-actuated piston adapted for reciprocal movement in the cylinder, a valve assembly in the main housing for normally preventing air under pressure in the chamber defined by the main housing from actuating the piston, said valve assembly including a normally closed main valve and a normally closed pilot valve, a pressurized air-actuated valve piston for opening the main valve, finger actuated trigger means for momentarily moving the pilot valve from its normally closed position to an open position, said trigger means being self-resetting upon release by the finger of an operator, passageway means communicating with the valve assembly and the chamber defined by the main housing for enabling air under pressure from the chamber to actuate the valve piston and open the main valve when the pilot valve is momentarily moved to an open position by the trigger means for actuating the piston, stunning means actuated by the piston for delivering an immobilizing blow, valve reseating means associated with the valve assembly for automatically returning the main valve and the pilot valve to their normally closed position, and a handle for the tool to enable an operator to support, aim and operate the tool with one hand.
 21. A stunning tool for use in immobilizing livestock comprising a main housing defining a chamber for receiving air under pressure from a source thereof, a cylinder joined to the main housing and extending into the chamber defined by the housing, a pressurized air-actuated piston adapted for reciprocal movement in the cylinder, a valve assembly in the main housing for normally preventing air under pressurE in the chamber defined by the housing from actuating the piston, said valve assembly including a normally closed main valve and a normally closed pilot valve, a pressurized air-actuated valve piston for opening the main valve, finger actuated trigger means for momentarily moving the pilot valve from its normally closed position to an open position, said trigger means being self-resetting upon release by the finger of operator, passageway means communicating with the valve assembly and the chamber defined by the main housing for enabling air under pressure from the chamber to actuate the valve piston and open the main valve when the pilot valve is momentarily moved to an open position by the trigger means for actuating the piston, stunning means actuated by the piston for delivering an immobilizing blow, piston return means for automatically resetting the piston after each successive power stroke, valve reseating means associated with the valve assembly for automatically returning the main valve and the pilot valve to their normally closed position, and handle means positioned on the main housing to enable the tool to be supported, aimed and operated while being held by both hands of an operator.
 22. A tool according to claim 22 wherein the stunning means includes a chisel-like blade member having a concave leading edge capable of performing a severing operation. 